1. Field of the Invention
This invention concerns a device for controlling the speed of a motor vehicle, and more particularly one which does not require engine vacuum to operate.
2. Description of the Prior Art
Speed or "cruise" controls are in widespread use. The speed control allows the driver to select a speed, and the control device will maintain the vehicle at the selected speed. Most speed controls use the engine vacuum to pull a piston in a chamber. The piston is connected to the throttle linkage. A vacuum valve closes to apply more vacuum if the speed drops below the selected level. A vent valve opens to release vacuum if the speed is above the selected level. A microcomputer chip monitors the speed and controls the valves.
While successful, in some cases, especially those with small engines, the vacuum supply is inadequate to control the speed. Electric motors are used in some cases for speed control in lieu of vacuum. They either use a sensitive stepping motor or a motor with gear drive and a clutch. These systems are expensive. Also, reliability can be a problem.